Roller-type ultrasonic inspection devices

Abstract

A roller-type ultrasonic inspection device for inspecting vehicle tires comprises a roller assembly 20 mounted on a non-rotatable hug 16. Two piezoelectric crystals 80,82 are mounted in the hub 16 such that their principal transmitting/receiving axes A and B converge generally radially outwardly of the hub. The angle between the axes A and B is selected such that when the roller assembly 20 is urged into rolling contact with the tread-bearing surface of a tire 90, the axes meet (allowing for refraction effects) in the body of the tire beneath the tread. This ensures that the device can detect defects in the body of the tire, and is relatively insensitive to the tread.

What is claimed is: 
     
       1. A roller-type ultrasonic inspection device for inspecting a vehicle tire, the device comprising a roller member which is rotatably supported on a non-rotating hub and which is adapted to make rolling contact with the tire, and first and second ultrasonic transducers which are mounted in said hub and which each have a principal transmitting and receiving axis, said transducers being electrically connected to cooperate with each other and being mounted in said hub such that said axes converge generally outwardly of said hub, the angle between said axes being selected such that when the roller member is placed in rolling contact with the tread-bearing surface of the tire and the device is operated as a transmitter, the transducers cooperate together to focus transmitted ultrasonic energy in the body of the tire beneath the tread, and when the device is operated as a receiver, the transducers are responsive to defects in the body of the tire beneath the tread. 
     
     
       2. A device as claimed in claim 1, wherein the first and second transducers are electrically connected in parallel. 
     
     
       3. A device as claimed in claim 1, wherein the first and second transducers each comprise a respective flat piezoelectric crystal. 
     
     
       4. A device as claimed in claim 3, wherein said crystals are substantially undamped. 
     
     
       5. A device as claimed in claim 3, wherein said crystals are of lead zirconate titanate. 
     
     
       6. A device as claimed in claim 3, wherein the first and second transducers are formed by splitting a single, substantially circular, piezoelectric crystal into two substantially symmetrical halves. 
     
     
       7. A device as claimed in claim 3, wherein the first and second transducers are mounted on respective flat surfaces on a common mounting member. 
     
     
       8. A device as claimed in claim 7, wherein said mounting member is made of aluminium. 
     
     
       9. A device as claimed in claim 7, wherein the included angle between said flat surfaces is less than 160°. 
     
     
       10. A device as claimed in claim 9, wherein said angle is about 120°. 
     
     
       11. A device as claimed in claim 7, wherein said mounting member is secured in a radially inwardly extending recess in said hub, with its radially outer surface machined to conform to the radially outer surface of the hub, said flat surfaces being formed on the radially inner surface of the mounting member. 
     
     
       12. A device as claimed in claim 11, wherein the portion of the recess radially inwardly of said transducers is gas-filled.